The invention relates to a connecting piece for conductively connecting poles of two batteries or battery cells, which has a base body with at least one recess, wherein at least one insert element is arranged in the inner region of at least one recess. The application further relates to a production method for such a connecting piece
Electrically driven motor vehicles have batteries, which are composed of individual battery cells. These are mostly lithium ion batteries, wherein the individual cells are formed by an anode and a cathode, which are respectively made of different materials. The individual cells are connected to each other in a serial connection in order to produce the required total voltage.
For this purpose the individual cells of a battery have to be connected to each other by way of connecting pieces. Hereby the respective anode of a cell and the cathode of the subsequent cell are connected with each other.
Anodes are often produced on the basis of an aluminum alloy, whereas cathodes are mostly based on a copper alloy.
The connecting pieces have to have a good electric conductivity, which makes copper a preferred manufacturing material. However, directly connecting a connecting piece made of copper with a battery contact made of aluminum poses the risk that in the presence of oxygen or humidity the contacting piece or the contact surface between the contacting peace and the battery contact corrodes and is thus destroyed.
This can be prevented by using identical materials at the contact site between the battery pole and the connecting piece (for example in each case aluminum). At the same time, however, the connecting piece has to possess the very good conductivity of copper.
Consequently, connecting pieces are known from the state-of-the-art who's connecting points are configured in correspondence with the material of the battery contact.
Thus for example from DE 10 2011 080 977 A1 a cell connector for electrically connecting terminals of battery cells is known, which is made of multiple material layers, wherein layers of a first material and a second material are alternately arranged. These materials can be copper and aluminum. The respective layers have two holes, wherein the holes in the copper layers are greater than the holes in the aluminum layers. These layers are arranged above each other so that smaller hole is arranged coaxial to the greater hole. As a result a connection site made of aluminum is formed in the inner region of the greater holes, so that when mounting the cell connector on the battery cells the aluminum poles can be connected with a contact region made of aluminum. In a vice versa arrangement also a connecting site for copper poles can be produced.
A disadvantage of such connecting pieces is on one hand the complex manufacturing, because a multitude of individual material layers has to be arranged precisely on top of each other. At the same time there is the risk of corrosion on between the individual material layers, which according to DE 10 2011 080 977 A1 is to be avoided by a plastic sealing. This sealing however represents an additional process step, which makes the production of such connecting pieces more complicated and more expensive.
A simplified manufacturing variant of a connecting piece for connecting two polls of cells of batteries is disclosed in DE 10 2007 063 177 A1. Here the connecting piece is made of a base body, which has two openings. In each of the two openings a sleeve-shaped compensation element is introduced, wherein the compensation element and the base body and the compensation element and the battery pole are connected to each other by a material-to-material connection.
Here, the production of the connection piece is strongly simplified, however, the welding connection of the inner sleeve made of aluminum or an aluminum alloy with a base body made of copper or a cooper alloy is difficult to produce. Nevertheless it is still required, however, to connect such a sleeve with the base body so that the sleeve is securely held in the base body.